.logo{
     /* width: 50px;
     height: 50px;
     position: absolute;
     left: 0;
     top:0; */
     background-image: url(https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1555482694157&di=a4c31263694ba5af2be54c44fff28710&imgtype=0&src=http%3A%2F%2Fmy.yingjiesheng.com%2Fupload%2F1703%2F9680563_1490838572.jpg);
     background-size: 100%;
     background-repeat: no-repeat;  
}
.tip{
     display: none;
}